The present teachings are predicated upon providing an improved parking brake assembly. For example, the parking brake assembly may be used with almost any brake assembly and/or almost any vehicle (e.g. car, truck, bus, train, airplane, or the like). Alternatively, the parking brake assembly can be integrated into one or more manufacturing assemblies requiring a brake, such as a lathe, a winder for paper products or cloth, amusement park rides, wind turbines, or the like. However, the present teachings are most suitable for use with a disc brake system or a drum brake system for a passenger vehicle (e.g., a car, truck, sports utility vehicle, or the like).
Generally, a brake assembly (e.g., a disc brake system) may include a primary brake assembly and a parking brake assembly. The primary brake assembly includes a rotor, a brake caliper, and inboard and outboard brake pads on opposing sides of a rotor. The brake caliper also includes one or more piston bores, each of which house a piston that moves along a piston axis during a brake apply and release of the brake apply. To create a brake apply, brake fluid can move the one or more pistons into contact with the inboard brake pad and then move the inboard brake pad into contact with one side of the rotor, while an opposing brake pad is moved into contact with the opposing side of the rotor. Another example of a primary brake assembly is a drum brake assembly that includes a pair of brake shoes in a drum. The brake shoes are moved into contact with an inner surface of the drum to create a brake apply.
When a vehicle is stopped or parked, the parking brake assembly may be used to prevent movement of the vehicle. The parking brake assembly may be a discrete assembly, or may utilize one or more components of the primary brake assembly. That is, the parking brake assembly may use the one or more of the pistons and the one or more brake pads of the primary brake assembly to create the brake apply. For example, the parking brake assembly may move the one or more pistons, which may move the one or more brake pads into contact with the rotor to create and maintain a brake apply.
Examples of various brake assemblies and parking brake assemblies are disclosed in U.S. Pat. Nos. 2,885,032; 3,809,191; 5,785,157; 5,913,390; 6,446,768; 6,684,988; 8,2920,080; in U.S. Patent Application Publication No. 2013/0087422; and in U.S. patent application Ser. No. 14/567,617 filed on Dec. 11, 2014, all of which are expressly incorporated herein by reference for all purposes. It would be attractive to have a parking brake assembly that can be used with any brake assembly, including a disc brake system. It would be desirable to have a parking brake assembly including a differential that can be unlocked in one configuration to create a brake apply and locked in another configuration to release a brake apply. During a brake apply, it would be attractive to have a differential that can distribute a rotational force to the output shafts until one of the output shafts experiences higher resistance, which then the differential can re-distribute the rotational force to the other output shaft. During release of the brake apply, it would be attractive to have a differential that can distribute an opposing rotational force equally the output shafts.